WPILib Swerve Code

rmeesters · October 12, 2022, 11:28pm

Looking over the Swerve Drive code sample from WPILIB (https://github.com/wpilibsuite/allwpilib/blob/main/wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/swervebot/Drivetrain.java). Most of it makes sense, but I’m struggling to understand what these lines do:

private final SwerveModule m_frontLeft = new SwerveModule(1, 2, 0, 1, 2, 3);
private final SwerveModule m_frontRight = new SwerveModule(3, 4, 4, 5, 6, 7);
private final SwerveModule m_backLeft = new SwerveModule(5, 6, 8, 9, 10, 11);
private final SwerveModule m_backRight = new SwerveModule(7, 8, 12, 13, 14, 15);

Any help on this would be most appreciated.

vargoose84 · October 12, 2022, 11:35pm

See this file (or below) for an explanation:

github.com

wpilibsuite/allwpilib/blob/main/wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/swervebot/SwerveModule.java

// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.

package edu.wpi.first.wpilibj.examples.swervebot;

import edu.wpi.first.math.controller.PIDController;
import edu.wpi.first.math.controller.ProfiledPIDController;
import edu.wpi.first.math.controller.SimpleMotorFeedforward;
import edu.wpi.first.math.geometry.Rotation2d;
import edu.wpi.first.math.kinematics.SwerveModuleState;
import edu.wpi.first.math.trajectory.TrapezoidProfile;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.motorcontrol.MotorController;
import edu.wpi.first.wpilibj.motorcontrol.PWMSparkMax;

public class SwerveModule {
  private static final double kWheelRadius = 0.0508;
  private static final int kEncoderResolution = 4096;

This file has been truncated. show original

  public SwerveModule( 
       int driveMotorChannel, 
       int turningMotorChannel, 
       int driveEncoderChannelA, 
       int driveEncoderChannelB, 
       int turningEncoderChannelA, 
       int turningEncoderChannelB) {

Oblarg · October 13, 2022, 3:00am

These should probably be named constants in that example…

SLAB-Mr.Thomas · October 13, 2022, 11:44am

GitHub does have some tools for finding references but often it still feels like a treasure hunt. For the same but easier to follow code, create a new Java Project for the SwerveBot example in your VSCode. You get the whole robot program at once and it’s easy to find references including referenced library classes.

If you hover over the second SwerveModule word in the line of code you show, the explanation shows immediately with the good Java doc explanation. Even if no Java doc had been provided, it’s still fairly easy to see the parameter list of the called method with nicely named variables.